Activity 3.3.1 Air Pollution Core Activity

Air Pollution Basics

• Sulfur Pollutants

According to the text, "the widespread use of coal led to severe pollution by sulphur dioxide (SO2) and soot in the industrial towns and cities of Europe and the Americas" (pg. 366 ch.16). SO2 is usually described as a colorless but pungent gas. "Humans can detect its bitter taste at a concentration of only 0.3-1 ppm (parts per million; for SO2, 1 ppm = 2.6 mg/m3" (pg. 368 ch.16). However, humans and most animals are much less sensitive to SO2 than plants are. Sulphate is formed when SO2 and H2S compounds become oxidized. SO2 can typically linger in the atmosphere for about four days (pg.368 ch.16). It is also apparent that "volcanoes are natural sources of emission of sulphur gases. On average, volcanoes emit about 12-million tonnes of sulphur gases per year, of which 90% is SO2 and 10% is H2" (pg.369 ch. 16). The global anthropogenic emissions of SO2 are about 150-million tonnes per year, which are released mostly through the burning of coal and petroleum (pg. 369 ch.16). In contrast, "clean air typically contains less than 0.2 ppb of SO2 or H2S. Concentrations of SO2 and H2S in air that is polluted by emissions are highly variable. They are typically about 0.2 ppm in urban atmospheres but can exceed 3 ppm close to large emission sources" (pg. 371 ch.16). These amounts of sulphur emissions differ amongst the nations but also correlates to their population, their kind of industrialization, and the fuels that they use.

• Nitrogen Pollutants

"The most important of the nitrogen-containing gases are nitric oxide (NO), nitrogen dioxide (NO2), nitrous oxide (N2O), and ammonia (NH3). NO and NO2 are often considered together as a complex, referred to as NOx" (pg. 373 ch.16). Natural emissions of NH3 are about 1.2-billion tonnes per year as the gas typically lingers in the air for about seven days (pg. 374 ch.16). Then there is nitrous oxide (N2O), which is a colorless, non-toxic gas otherwise known as “laughing gas” and is used as "a mild anesthetic in medicine, and sometimes as a recreational drug (pg. 374 ch.16).  Because N2O is a

more unreactive than other nitrogen pollutants, it can linger in the atmosphere for about four years. Agricultural soil fertilized with nitrate can have high rates of N2O emission, and modern agricultural practices are thought to have increased global emissions by about 40%. "Nitric oxide (NO) is a colorless and odorless gas, while nitrogen dioxide is reddish, pungent, and irritating to

respiratory and eye membranes" (pg. 374 ch.16). 

• Hydrocarbon and Volatile Organic Compound Pollutants

Hydrocarbons are chemicals with molecular structures containing various combinations of hydrogen and carbon atoms. The simplest hydrocarbon is methane (CH4), a gas. Larger hydrocarbons with more complex structures usually occur as vapors, liquids, or solids. Other volatile organic compounds (VOCs) may contain oxygen, nitrogen, and other light elements in addition to carbon and hydrogen, and include alcohols, aldehydes, and phenols (pg. 374 ch.16). "Most emissions of CH4 are natural and are associated with the fermentation of organic matter by microbes in anaerobic wetlands. Smaller amounts are outgassed from deposits of fossil fuels, during wildfires, and from burping and flatulent ruminant animals (such as cows and sheep) and termites, which produce CH4 as they digest their plant foods" (pg. 375 ch.16). There are also non-methane hydrocarbons, and the largest emissions of these pollutants come from forests and typically occur during hot, sunny days or the summer season.

Comparison of Current AQI

	Time of Day	AQI Current	AQI Forecast	PM2.5	O3
Plains Montana CT (highest)	10:00 pm	111	74	39	73
San Antonio, TX (Where I Live)	10:00 pm	60	Moderate	16	57
Los Angeles, CA	10:00 pm	38	116	9	41

• The AQI or, Air Quality Index, tells you how clean or polluted your air might be. The higher your number is, mean that there is a greater amount of pollution in the air. Which is important to keep track of because certain AQI numbers could signal any potential health risks that might rise because of the polluted air. The AQI scale runs from 0 to 500, 0 being perfectly clean and safe (which might be rare), while 500 is completely hazardous. An AQI value of 100 serves as the national air quality standard for the pollutant. A value of or between 0 to 50 means the air quality is good/safe. A value of or between 51 to 100 means the air quality is moderate or satisfactory, its set as the typical air quality goal for public safety. 101 to 150 is labeled as unhealthy for sensitive groups. 151 to 200 is overall unhealthy. 201 to 300 is very unhealthy, while 201 to 500 is as previously mentioned, very hazardous. 

Comparison of Current PM2.5 and O3 to EPA Standards

National Standard	San Antonio Current measured over 1 hour	Time of Day
PM2.5 Average measured over 24 hours - 35 μg/m3	17.9 µg/m3	11:30 pm
O3 Average measured over 8 hours - 70 ppb (137 µg/m3)	36 ppb	11:30 pm

• PM, or particulate matter is anthropomorphic, meaning that it is generated by humans. PM in the United States is measured and regulated by the federal Environmental Protection Agency (EPA). The different regulations we can monitor are on PM2.5 and PM10. PM2.5 is particulate matter that is literally 2.5 microns or less in size. Obviously, we can't see this matter unless it's concentrated in the air. Then there is PM10, which is less than 10 microns that we can see in the air. Because PM 2.5 is so small, it can be dangerous to our health since it tends to stay in the air longer than heavier particles and therefore, travels into our circulatory and respiratory systems. It can be as serious as causing premature death from heart and lung disease. PM is commonly released through industrial and gas emitting/burning processes.

• O3, formally translated into the element trioxygen, is another form of an air pollutant. The broadest term for this element is the ozone. Ozone comes from cars, power plants, boilers, refineries, and other common industrial or machine processes. Like PM, this pollutant can also harm the respiratory system by constricting muscles in the airway and causing shortness of breath or coughing/ sore throats. 

 

Sources:

Freedman, B. (2018). Environmental science: A Canadian perspective. Halifax, Canada: Dalhousie University Libraries.

US Environmental Protection Agency (EPA). (2019, June 18).Air quality index basics. Air Now. https://airnow.gov/index.cfm?action=aqibasics.aqi